Abstract

New data on the inheritance of progressive familial heart block type 1 (PFHB1) does not favour the theory that the original immigrant (founder of PFHB1 families) introduced the genetic abnormality into South Africa and suggests that a new mutation in family member b6 (Fig. 1) was possibly responsible for the origin of the disease. If the mutation occurred in family member b6, this would reduce the number of affected family members from a previously estimated 9 000 to a mere 860 with a revised prevalence of 1:5 000 South Africans of European descent.